Novel methodologies for addressing regeneration challenges in styrene-saturated activated carbon for styrene removal

Activated carbon (AC) adsorbents are extensively utilized for the adsorption and elimination of volatile organic compounds (VOCs), such as styrene, owing to their remarkable adsorption capacity and cost-effectiveness. However, the regeneration and reutilization of activated carbon face significant limitations due to incomplete cleavage of styrene and carbon accumulation during heated styrene cracking. This research focuses on the preparation of Ni-Fe bimetal-enriched adsorbent columns by successfully loading transition metals Ni and Fe onto activated carbon saturated with styrene adsorption using a simple impregnation method. A series of characterizations were conducted to unveil the formation process of active sites in the alloy phase and the mechanism behind the synergistic anti-accumulation effect of Ni and Fe on carbon deposits. Furthermore, the adsorption performance of the regenerated activated carbon for styrene was evaluated. The results revealed the formation of Fe 0.64 Ni 0.36 and Ni-Fe alloy (Kamacite) phases on the activated carbon carriers, which enhanced the cracking of styrene and exhibited superior anti-carbon accumulation properties. The styrene adsorption capacity of the synthesized bimetallic 2.5Fe-2.5Ni-900 regenerated sample reached 407.5 mg/g, approximately 1.5 times higher than that of the monometallic samples 5Fe-900 and 5Ni-900, and 1.6 times higher than that of the unmodified activated carbon RAC-900. Furthermore, kinetic studies indicated that the adsorption process of styrene by the samples followed a multilayer adsorption mechanism, predominantly governed by physical adsorption. Intra-pore diffusion was identified as the primary rate-determining step during the adsorption process. Moreover, after three regenerative adsorption cycles, the decrease in styrene adsorption capacity for the 2.5Fe-2.5Ni-900 sample was below 20 %. This study presents novel perspectives and methodologies for addressing the regeneration challenge of activated carbon saturated with styrene adsorption.